Jack LeRoy Christiansen (December 20, 1928 – June 29, 1986) was an American professional football player who became a college and pro coach.

[3] He concluded his career as an assistant coach for the Kansas City Chiefs (1977), Seattle Seahawks (1978–1982), and Atlanta Falcons (1983).

Christiansen was born in Sublette, Kansas, in 1928,[4] and was raised an orphan at the Odd Fellows Orphanage in Cañon City, Colorado.

[14] At the end of the season, he was selected by the AP and United Press International (UPI) as a first-team All-NFL player and was invited to play in the Pro Bowl.

He continued this high standard of play, tying for the interception lead with 10 picks-six in 1957 to help the Lions win their third title in six years.

He was an All-NFL defensive back for six-straight years, played in five Pro Bowls (opening the 1956 game with a 103-yard kickoff return) and led the league in interceptions twice.

[16][17] In that season's final 11 games, the 49ers won only twice, but held the distinction of being the only team to defeat the eventual NFL champion Chicago Bears.

In January 1968, Christiansen was hired by his alma mater, Colorado State, as a consultant to review and make recommendations concerning the university's athletic program.

[20] During this period, Stanford pulled off consecutive Rose Bowl upsets of Ohio State and Michigan, both previously undefeated.

[22] In March 1977, Christiansen was hired as an assistant coach, responsible for running backs, under Paul Wiggin with the Kansas City Chiefs.

In April 1978, Christiansen was hired by the Seattle Seahawks, replacing Bob Holloway as the team's defensive backfield coach.